Don't log behavior-related messages if no behaviors are set

[tw4l]

Related to webrecorder/browsertrix#1963 (review)

When the behaviors argument is set to an empty list (meaning no behaviors), we should not log behavior-related messages such as "Running behaviors", "Run Script Started", and "Waiting for behaviors to finish" among others.

Their presence is confusing noise if behaviors are disabled.

[ikreymer]

Yeah, I think we should make sure we disable the execution of browsertrix-behaviors altogether if all behaviors are disabled, that may not be the case..